A proton exchange membrane (PEM) fuel cell, also known as a polymer electrolyte membrane (PEM) fuel cell, uses fuel, e.g., hydrogen, and oxidant, e.g., oxygen, to produce electricity, transforming the chemical energy liberated during the electrochemical reaction of the fuel and oxygen into electrical energy. A PEM fuel cell generally employs a membrane electrode assembly (MEA), which includes a PEM disposed between two porous electrically conductive electrode layers. An electro catalyst is typically disposed at each membrane/electrode layer interface to induce the desired electrochemical reaction. In a typical PEM fuel cell, the MEA is disposed between two electrically conductive separator plates. Each separator plate employs a fluid flow field that directs the fuel or the oxidant to the respective electro catalyst layers.
A simple fluid flow field may include a chamber open to an adjacent porous electrode layer with a first port serving as a fluid inlet and a second port serving as a fluid outlet. More complicated fluid flow fields incorporate at least one fluid channel between the inlet and the outlet for directing the fluid stream in contact with the electrode layer or a guide barrier for controlling the flow path of the reactant through the flow field. The fuel stream directed to the anode by the fuel flow field migrates through the porous anode, and is oxidized at the anode electro catalyst layer. The oxidant stream directed to the cathode by the oxidant flow field migrates through the porous cathode and is reduced at the cathode electro catalyst layer.
Various designs of the flow field have been developed. For example, a Conventional Flow Field (CFF) design uses a number of channels between an input and an output and is configured to provide a relatively uniform reactant distribution on the electrode. In this conventional configuration, the reactant flowing in the channels may distribute into the electrode and react with the other reactant. However, some reactant may flow directly from the input to the output, without entering into the electrode, and therefore, the reactant utilization rate is relatively low. To increase the reactant utilization efficiency, an Interdigitated Flow Field (IDFF) design has been developed. An IDFF includes a set of inlet flow channels and a set of outlet flow channels, and the inlet flow channels are not connected to the outlet flow channels. In an ITFF, the reactant gas in the inlet flow channels is forced into the adjacent porous electrode and the chance for the reactant gas to contact with the catalyst is increased, and thereby, the reactant utilization efficiency is increased. The IDFF configuration can provide higher cell performance and lower fuel consumption as the fuel gas is more efficiently diffused to the electrodes. However, the IDFF configuration also has some disadvantages. For example, in an IDFF, the membrane electrode assembly might be more easily dried out, particularly when the fuel cell operates at a high temperature.
Therefore, there remains a need for a new flow field design for a fuel cell that can increase the fuel cell overall performance.